E. Marinades

Marinades are similar to brines in most ways: They are liquid, they are flavorful, and they infuse their flavors into solid ingredients by opening up tightly wound proteins. The big difference is that their active ingredient is acid, rather than salt. The acid can be almost anything—vinegar, citrus, fruit juice, wine, buttermilk, yogurt, tea, or coffee—and although each brings a different flavor to the mix, they all work in the same way.

Keep in mind that the atoms of all substances are in flux. The formula for water is H2O, and most of the molecules in a cup of water are in that form. But at any given moment, there is a small percentage of molecules that break into positively charged hydrogen ions (H+) and negatively charged hydroxyl groups (OH–). The free H+ atoms could join with an OH– and form back into water, or they could bond to another water molecule, forming a positively charged H3O molecule. Under normal conditions, very little of this is going on, but if enough H+ ions start floating around, the whole mixture and anything in its vicinity could become unstable. Our bodies are designed to keep this from happening, so we have developed the ability to recognize any substance that releases H+ ions into the environment. We taste them as sour, and we call them acids. The more positive ions an acid releases, the stronger it is.